Electric tools are provided with handles for operating them. Drills or pneumatic drills, for example, are provided with a handle that permits the electric tool to be held in the working position. This handle is frequently associated with an on-off switch and/or other controls. In the broadest sense, therefore, the handle is used to operate the electric tool. It permits the electric tool to be held in the working position, a force to be exerted, in particular along the central axis of the device and therefore parallel to the axis of a tool being used, for example a drill bit, and a torque to be exerted, which is used as a reaction torque opposing the torque resulting from the rotation of the tool when a load is placed on it.
In addition, auxiliary handles are known, which permit a two-handed operation of an electric tool. The main handle, which is usually situated at the end of the electric tool oriented away from the insert tool, is held with the one hand. This hand also operates the electric switch device, which is usually accommodated in this handle. In order to provide support, particularly in high-torque machines and in applications in which a powerful torque is exerted on the operator, for example when drilling with large diameters, when using annular drill bits, or when using the electric tool as a drive unit for a mixer, an auxiliary handle is provided, which permits the operator to also exert an assisting reaction torque with his other hand. Usually, this auxiliary handle is attached to the front end of the electric tool, i.e. the end associated with the tool-receiving socket. The handle is usually mounted either by means of an internal thread provided inside the machine, for example in the collar of the machine, or (more universally) through the use of a clamping strap or clamping device that is associated with the auxiliary handle and is slid over the collar of the machine and locked by means of a screw clamping mechanism.
A feature common to these handles known from the prior art is that they cannot be used for functions other than those mentioned above, namely holding the electric tool in a particular working position and exerting forces and/or a torque.
Specifically in high-torque electric tools or in electric tools that exert very powerful forces on the work piece, for example pneumatic drills, it is known that safe handling requires two-handed operation. The electric tools known from the prior art with the handles known from the prior art always supply the same output to the tool-receiving socket regardless of whether one or two handles are mounted and regardless of whether the operator is working with one or two hands. It is therefore possible, with the sudden occurrence of a spike in torque, for the electric tool to be thrown from the operator's hands. This is particularly the case if the insert tool, for example a large diameter drill bit or annular drill bit, jams in the work piece and the torque causes the machine to start rotating around the drill bit axis. If the user is not prepared for these abruptly occurring spikes in torque and is only holding the machine e.g. with the main handle at the rear end of the electric tool, then the rotation can easily throw the machine from the hand holding the electric tool, which can cause injuries to the operator. In particular, it is also possible here for the machine to slip out from the work piece and damage the work piece during the time that the insert tool and the driven tool-receiving socket are coasting to a final stop from the running state. It is also possible for it to damage nearby objects and injure the user himself.
Current designs for safely operating an electric tool known from the prior art by exerting the required reaction forces and the required reaction torque are only effective if the operator uses them conscientiously. Experience has shown that particularly with operators who regularly and routinely use electric tools, there is a significant degree of habitual negligence with regard to careful, safe practices with electric tools. For example, even high-powered and high-torque electric tools are often casually held with one hand or auxiliary handles are not even installed because an auxiliary handle has a natural tendency to lend the machine a slightly less agile feel.